1. Field of the Invention
The present invention relates generally to an apparatus for treating and destroying harmful cells within the body. More particularly, the present invention relates to an apparatus for delivering heat and radiation to a tumor within a body to destroy the cells in the tumor.
2. Background Art
Hyperthermia, the heating of body cells to above 41° C. for therapeutic purposes, particularly to destroy cancer tumors, has been known and used in the past. It is also known that above 46° C., irreversible destruction of healthy and diseased body cells occurs. The purpose of hyperthermia equipment generally is to deliver heat preferentially to diseased body cells while maintaining adjacent healthy cells at acceptable temperatures, i.e., below the temperature at which irreversible cell destruction occurs.
There are three main theories which explain why hyperthermia is successful in fighting cancerous growths. Some scientists believe that heat produces a localized fever which causes lymphocytes to congregate (200 lymphocytes are usually needed to destroy one cancerous cell). Other scientists think heat improves the flow of blood in the tumor, and this increased blood flow, in turn, brings more oxygen to the tumor and lowers its Ph, thus starving the tumor cells by reducing nutrients. A third theory contends that the DNA forces that hold tumorous cells together are weaker than those of healthy cells and the heat applied to the tumorous cells breaks them apart and thereby destroys them more easily.
Hyperthermia or induced high body temperature is beneficial in treating many types of cancer. Some malignant cell masses having poorer heat dissipation characteristics than normal tissue, presumably due to abnormally low blood circulation, are subject to preferential hyperthermia treatment. As a result, such malignant cell masses can often be heated to temperatures substantially higher than that of surrounding healthy cells, to enable hyperthermia treatment, even when both types of cells are heated simultaneously. This characteristic not only enables hyperthermia treatment of some types of malignancies which are no more temperature sensitive than normal cells, but usually permits much shorter hyperthermia treatment times, even of thermally sensitive malignancies, as is important for various medical reasons.
More specifically, various types of malignant growths are considered by many researchers to have a relatively narrow hyperthermia treatment temperature range. Below a threshold temperature of about 41.5° C. (106.7° F.), thermal destruction of these malignancies is not believed to occur. In fact, for hyperthermia temperatures below this threshold, growth of some of these malignancies may tend to be stimulated. In contrast, at temperatures above a range of about 43° C. to 45° C. (109.4° F. to 113° F.) thermal damage even to most normal cells occurs, the exposure duration at any elevated temperature also being a significant factor. Accordingly, if large or critical parts of a human body are heated into, or above, the 43° C. to 45° C. range for even relatively short durations, serious permanent injury or death is possible.
Radiation treatment of malignant cells is also known. Radiation treatment is classified into two general categories. Teletherapy is treatment of cells within a body from an area external to the body. Radiation generated outside the body travels through the body to reach the malignant cells when the malignant cells are on the interior of the body. Thus, healthy cells are exposed to harmful, cell killing radiation. One way to minimize exposure of a cell at a specific point is to focus radiation over an area at the source to a point distant from the source, where the cells to be treated are at the focal point. In this way, only the malignant cells are exposed to the full power of the radiation. However, healthy tissue surrounding the malignant cells, and all cells between the malignant cells and the radiation producing device are still exposed to a large amount of radiation.
Brachytherapy, a second type of radiation treatment, is treatment of cells from a point or source on the interior of the body. Thus, brachytherapy has the advantage of allowing localized radiation treatment. A physician can treat malignant cells by radiating in an area in close proximity to, or within, a group of malignant cells such as a tumor, with only minimal exposure to radiation of healthy cells.
Recently, it was discovered that hyperthermia and radiation, used in combination, is more effective at killing malignant cells than either hyperthermia or radiation alone. Hyperthermia suppresses the repair mechanism of the cellular DNA which is damaged by ionizing radiation. At normal body temperatures, the time required for a cell to complete repair is about 30-45 minutes. At elevated temperatures, in the range of 42-45° C., the repair mechanism is disabled. Thus, while at elevated temperatures, the cell cannot repair the damage to the tumor caused by the radiation exposure. Therefore, the amount of radiation necessary to break down the tumorous cell is greatly reduced.
Currently, hyperthermia is used with radiation to treat malignant cells by using the combination of localized hyperthermia treatment to heat the cells, and teletherapeutic treatment to radiate the cells. Despite the advantages of treating malignant cells with both heating and radiation, there is not a brachytherapeutic apparatus capable of delivering both X-ray radiation and interventional heating to a malignant tumor. Therefore, what is needed is an apparatus that is capable of providing brachytherapeutic X-ray radiation and interventional heating to a malignant tumor.